The present invention relates generally to a system for feeding substantially flat articles and, more specifically, to an article feeding system having a feeding surface with a low-coefficient friction surface.
In a typical flat article feeding system, such as an envelope insertion machine for mass mailing, there is a gathering section where the enclosure material is gathered before it is inserted into an envelope. This gathering section includes a gathering transport with pusher fingers rigidly attached to a conveying means and a plurality of enclosure feeders mounted above the transport. If the enclosure material contains many documents, these documents are separately fed by different enclosure feeders. After all the released documents are gathered, they are put into a stack to be inserted into an envelope in an inserting station. At the same time, envelopes are sequentially fed to the inserting station, and each envelope is placed on a platform with its flap flipped back all the way, so that a plurality of mechanical fingers or a vacuum suction device can keep the envelope on the platform while the throat of the envelope is pulled away to open the envelope.
Before envelopes are fed to the insertion station, they are usually supplied in a stack in a supply tray or envelope hopper. Envelopes are then separated by an envelope feeder so that only one envelope is fed to the insertion station at a time. For that reason, an envelope feeder is also referred to as an envelope singulator. In a high-speed insertion machine, the feeder should be able to feed single envelopes at a rate of approximately 18,000 No. 10 envelopes per hour. At this feeding rate, it is critical that only a single envelope at a time is picked up and delivered to the insertion station.
At a feeding period approximately equal to 200 ms, there are roughly 30 ms available for the feeder to reset before the next feed cycle is initiated. If an envelope is not present in close proximity before the next feed time, acquisition of the next envelope will not occur and a feed cycle will be missed, resulting in a reduced machine throughput.
The first aspect of the present invention is a hopper for flat articles having an upstream end and a downstream end for providing a stack of flat articles to an article feeder located near the downstream end. The article hopper includes a first bottom rod having a first rotation axis substantially parallel to a moving direction, running from the upstream end to the downstream end. At least one second bottom rod is co-located on a plane with the first bottom rod in order to form a supporting surface to support the stack of flat articles. A paddle is provided behind the stack of flat articles and is pivotally mounted at a pivot located above the supporting surface, for urging the stack of flat articles to move along the moving direction towards the article feeder. And further provided is a scrub wheel, having a second rotation axis, rotatably mounted on the paddle and positioned to make contact with the first bottom rod, with the second rotation axis being oriented at an angle relative to the first rotation axis, wherein the first bottom rod is adapted to rotate along the first rotation axis, causing the scrub wheel to rotate along the second rotation axis in response to the rotation of the first bottom rod, thereby producing an urging force on the pushing device towards the downstream end.
Preferably, the second bottom rod also rotates in order to reduce the friction between the stack of flat articles and the supporting surface. The flat article hopper also preferably has a side rod parallel to the rotation axis and is located above the supporting surface for registering the stack of flat articles, and the side rod is adapted to rotate in order to reduce the friction between the stack of flat articles and the side rod. The supporting surface is preferably titled from the horizontal surface, urging the flat articles to move toward the side rod in order to register against the side rod. The pivot is preferably located above the supporting surface and on the opposite side of the side rod.